I am looking to install a new exhaust on my 128i, but I thought it would be cool to install a dual exhaust. Has anyone seen or been succesfull doing this? Help please... Or just recommend me a good exhaust.

There is a German company offering quad exhaust pipes for 125i's (128i's). Just try searching for it. They were super pricey though! Like $2.5K I think. ? The reason why it was so much was bc they also sold you a cf diffuser too!

Some guy with a 135i bought one... he had it on his car for a few days before getting his money back and switching back to OE. The small-er 125i dia pipes killed his mid and top end. lol

I been looking for exhaust for awhile and really haven't pulled the trigger yet but after hearing the BMW PE it's sound pretty good. I been quoted $800 -1000 for custom exhaust. I'm assuming your 128i is non m-sport then you would need a new bumper and diffuser which is going to cost you some dough. If you got the m-sport then as flinchy said a decent quad diffuser is going to cost you.

I like dual exhausts - either spread apart on both sides of the car or in the center - but when you see this on 4 cylinders it makes it definitely less special. The miata is set up with dual spaced apart exhausts as is the base Altima 2.5. There are probably others. It seems more practical to get the BMW "performance exhaust" for more sound or the Magnaflow cat back for more flow and sound.